More power when cold?

[YAMASAKI]

Ok, I have a TR50 street magic, it has ahad a few things done to it to help it's performance... 70cc kit. Burial Blaze exhaust, 21mm Carb etc.

I live up a big hill (Brooklyn for wellingtonians) and I have found that it goes up at 50kph sweet when it is dead cold (the engine not the weather) but when warm it struggles to do 40...
It does good wheelies when cold too, but not when warm.

Anybody got any ideas as to what could be the issue? I'm not sure whether its the transmission or the motor itself.

[DELLORTO]

its the opposite with my 2 smokers........get a polini pipe then you'll be doing 60km/h up it...... my rm85 is way faster when its hot.....the powrband takes ova....

[carver]

my 2 strokes have been the same, i think its a expansion of moving parts thing

[skidMark]

It's running hot because it is too lean not getting enough fuel, or maybe your fuel mix ratio is not correct.

[piston broke]

is the fuel vapourising before it explodes perhaps?

[skidMark]

is the fuel vapourising before it explodes perhaps?

If its lean enough then yeah.....

[YAMASAKI]

It's running hot because it is too lean not getting enough fuel, or maybe your fuel mix ratio is not correct.

thanks for the input guys.
I'm running a 50:1 premix(which i was told was correct by the previous owner). I don't think it's running lean, the plug looked fine, if anything it is a bit rich (my first thoughts were that it was too rich when warm).
Compression is good. The guy at the shop thinks it my be crank seals letting air in (someone care to explain?) or carb issues, will book it in this week for some further investigations.

[skidMark]

thanks for the input guys.
I'm running a 50:1 premix(which i was told was correct by the previous owner). I don't think it's running lean, the plug looked fine, if anything it is a bit rich (my first thoughts were that it was too rich when warm).
Compression is good. The guy at the shop thinks it my be crank seals letting air in (someone care to explain?) or carb issues, will book it in this week for some further investigations.

Try run ya premix at 40:1

too rich will not cause a 2 stroke to run hot.

[haimsadia]

same here.. mine does power wheelies ( TR110) the 110cc version when hot it is just normal still goes pretty well though but no power wheelies... it's stock standard.

[SS90]

This is a bit of a "thread dredge"....

But I think it prudent to simply ignore all the answers on this subject thus far.

It would seem that the opening poster has a modified engine (including carb and main jet)

If you modify a two stroke, and, are then required to "increase the main jet size", 99% of "home tuners" put a mainjet in that would be about 50% bigger than required.
If you do (put too big a mainjet in), when the engine gets to "N.O.T" (normal operating temperature), the main jet will then be too big, and lose power.

Like if you leave the choke on.

Just like in all the examples given.

It would seem that many "keyboard tuners" mistake their poor knowledge of tuning with "oh yea, wow, now it make so much power it gets too hot and power fades"

When simply correct jetting is required.

In short, the OP's engine is jetted too rich. (too big main jet)

[YellowDog]

Ok, I have a TR50 street magic, it has ahad a few things done to it to help it's performance... 70cc kit. Burial Blaze exhaust, 21mm Carb etc.

I live up a big hill (Brooklyn for wellingtonians) and I have found that it goes up at 50kph sweet when it is dead cold (the engine not the weather) but when warm it struggles to do 40...
It does good wheelies when cold too, but not when warm.

Anybody got any ideas as to what could be the issue? I'm not sure whether its the transmission or the motor itself.

If you want to completely faaaark your engine, just carry on hard revving it hard whilst it is still cold.

As has already been said, playing with the timing and mix will resolve your issues.

Good luck.

[YAMASAKI]

geez, this is an old thread. the scoot has long gone.
SS90, i agree with what you say, however all my work was done at the scooter shop and I wouldn't have gone near the carb myself, my knowledge of two stroke tuning is somewhat lacking. What you have suggested pretty much sums up my initial thoughts, in that it was running too rich when warm. The guys at scooterazzi were adjusting jet sizes when i sold it on, with some definite improvements.

and YellowDog, it wasn't a case of me constantly giving it a handful of throttle on a dead cold motor, i do have some mechanincal sympathy (agreed, not like most scooterists out there , including the guy i sold it to :S). It was just an observation that it had significantly more power when cold, and popped the front up easily even at low revs.

[haimsadia]

any idea how you adjust the mixture and or if i should take it somewhere to have looked at? or is it just a waste of time giving it to like a shop? ( up here in auckland)




yes this is an old thread but i didnt want to start a new one ...

[SS90]

Air fuel mixture at anything above idle is controlled by jet sizes (bigger or smaller hole)

I really do suggest that if you have 0% knowledge or confidence then you must take it to a shop.

Be warned, it will co$t, BUT, if you find the right shop, they will be able to solve your problem.

Is it "stock" ?(are you 100% certain of that?, I mean, have you had it from new?

If there is really noticeable "power fade" from cold to hot, when it comes to CVT (constantly variable transmission) symptoms of "losing power when hot", can often be more than one problem.

How many K's does it have on it?

When did you last get a transmission service done?

Another problem that will cause a power loss from cold to hot (remember this is a modern engine, and is VERY well cooled) is the rollers in the front variator.

When these rollers get worn, they develop small flats on the edges, and when these rollers expand from the heat of normal operation, the won't quite return to the inner (lower ratio) position as quickly as they should.

The result is an engine that, when hot and under load (up a hill, stop/start), gives the impression of losing power..... when in actual fact, the transmission is unable to "go down to a low enough gear".....kind of like only having 2nd gear.

[haimsadia]

So Replaceing the rollers would be a good idea?

The bike was registerred in 2006 and i've owned it for about 8months .
It's done about 13,000km and i've put on it 6,000km......
I do have comfidence to work on it myself as i'm mechanically inclined and have a long history with cars. The only thing that i dont know is how to adjust the fuel ratio....

Secondly what do you mean by transmission service? do you mean just change the fluid inside? if so, i can definitly do that....